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Ensuring Moisture Protection
for Manufactured
Stone Drainage and drying for
absorptive claddings
by Jeff Diqui, Arch. Eng., CSI
All images courtesy Sto Corp.
FAILURES OF CLADDINGS LIKE ADHERED
MASONRY VENEER–ALSO KNOWN AS
MANUFACTURED STONE–OFTEN STEM
FROM POOR FLASHINGS, MISAPPLIED
AIR AND WATER-RESISTIVE BARRIERS
(WRB S ), AND LIMITED DRAINAGE.
RESULTING PROBLEMS RELATED TO MOISTURE
INTRUSION INTO THE WALL ASSEMBLY’S
DRY ZONE ARE MOIST WALL INTERIORS,
WET INSULATION, AND ROT IN SHEATHING
AND FRAMING.
Experience has shown detailing ﬂaws in cast-stone
veneer causes leaks which can lead to severe damage
inside the wall. Rain and wind are often the culprits.
A related effect in adhered masonry veneer cladding
is inward vapor drive, which can occur in warm
weather. It forces moisture stored in the masonry
through vapor-permeable housewraps and building
papers and into the sheathing and stud bay. This
can lead to condensation and water accumulation
within walls, as well as wood decay and condensation
on interior surfaces. 1
Some have assumed WRBs between claddings and
sheathing layers prevent moisture damage. Research
and ﬁeld experience demonstrate the WRB alone
may not always sufﬁce. 2 Common practices, such
as using double layers of housewraps or asphalt-
impregnated papers behind the absorptive claddings,
are shown to be ineffective under some climate and
weather conditions, particularly if poorly constructed
details allow excess water into walls.
12 the construction speciﬁer | january 2013
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